An Examination of the Coordination Chemistry of L2Pt(1,2-DITHIOLENES) Using Atmospheric Pressure Chemical Ionization Mass Spectrometry

Abstract

Atmospheric pressure chemical ionization mass spectrometry (APCI–MS) has been utilized in the characterization of two series of platinum dithiolene complexes, (COD)Pt(dt) 1, (COD)–Pt(edt) 2, (COD)Pt(dmid) 3, (COD)Pt(mnt) 4, (COD)Pt(eddo) 5, (COD)Pt(dddt) 6 and (Ph₃P)₂Pt(dt) 7, (Ph₃P)₂Pt(edt) 8, (Ph₃P)₂Pt(dmid) 9, (Ph₃P)₂Pt(dmit) 10, (Ph₃P)₂Pt(mnt) 11 (where COD = 1,5–cyclooctadiene, dt = ethane–1,2–dithiolate, edt = ethylene–1,2–dithiolate, dmid = 1,3–dithiole–2–oxo–4,5–dithiolate, dmit = 1,3–dithiole–2–thione–4,5–dithiolate, mnt = maleonitrile–1,2–dithiolate, eddo = 4–(ethylene–1′,2′–dithiolate)–1,3-dithiole–2–one, and dddt = 5,6–dihydro–1,4–dithiin–2,3–dithiolate). The series that contains triphenylphosphine is labile toward the loss of HPPh₃ ⁺. In addition, an orthometallated species involving the platinum and triphenylphosphine is identified. A dimer is identified for 2, which is shown to be a product of the experiment and not present in the parent material. In addition, a 1:1 adduct with NH₄ ⁺ is identified for 4 and 11 where the NH₄ ⁺ originates from the acid hydrolysis of acetonitrile. Finally, a highly unique ion, Pt⁺, a bare platinum ion, is observed in all COD complexes indicating that a radical mechanism must accompany the decomposition of the COD complexes during the fragmentation process.     

Reduction of Phosphine Oxide by Using Chlorination Reagents and Dihydrogen: DFT Mechanistic Insights

Extensive DFT calculations provide detailed mechanistic insights into the metal-free reduction of phosphine oxide Ph₃P=O by using chlorination reagents O=CClX (X=COCl, Cl, OCCl₃ and Ph) and H₂. Fast electrophilic attack to the P=O group oxygen atom is favored by exergonic CO₂ release to form phosphonium Ph₃PCl⁺ and chloride Cl⁻, which may slowly cleave H₂ by an unstable HPh₃PCl complex yielding Ph₃PH⁺ and Cl⁻ ions in solution. Moderate heating is required to accelerate the slow H₂-activation step and to eliminate HCl to form phosphine Ph₃P instead of Ph₃PH⁺Cl⁻ salt as the desired product. Though partially quenched by Ph₃P (and reactant Ph₃P=O if present), borane B(2,6-F₂C₆H₃)₃ can be still combined with Cl⁻ and Ph₃P as reactive frustrated Lewis pair (FLP) catalysts.     

Cyclopentadienylcobalt Complexes Containing Two Phosphine Ligands

The ionic complexes [C₅H₅Co(L)(Ph₂PMe)I]⁺ [I]^- (L = Ph₃P and Ph₂PMe) were prepared by the reactions of cyclopentadienyl(triphenylphosphine)cobalt and cyclopentadienyl(methyldiphenylphosphine)cobalt diiodides with methyldiphenylphosphine. The treatment of these complexes with sodium tetraphenylborate results in the formation of [C₅H₅Co(L)(Ph₂PMe)I]⁺[BPh₄]^- compounds.     

The hydrolysis of bromodifluoromethyltriphenylphosphonium bromide [1]

Hydrolysis of [Ph₃$\text{P}\text{+}$CF₂Br]Br^? afforded a high yield of bromodifluoromethane and triphenylphosphine oxide. Hydrolysis in the presence of a radioactive isotope of bromine or sodium iodide gave unequivocal evidence that the mechanism for this reaction proceeds through a difluorocarbene intermediate.     

A Systems Approach to a One-Pot Electrochemical Wittig Olefination Avoiding the Use of Chemical Reductant or Sacrificial Electrode

An unprecedented one-pot fully electrochemically driven Wittig olefination reaction system without employing a chemical reductant or sacrificial electrode material to regenerate triphenylphosphine (TPP) from triphenylphosphine oxide (TPPO) and base-free in situ formation of Wittig ylides, is reported. Starting from TPPO, the initial step of the phosphoryl P=O bond activation proceeds through alkylation with RX (R=Me, Et; X=OSO₂CF₃ (OTf)), affording the corresponding [Ph₃POR]⁺X⁻ salts which undergo efficient electroreduction to TPP in the presence of a substoichiometric amount of the Sc(OTf)₃ Lewis acid on a Ag-electrode. Subsequent alkylation of TPP affords Ph₃PR⁺ which enables a facile and efficient electrochemical in situ formation of the corresponding Wittig ylide under base-free condition and their direct use for the olefination of various carbonyl compounds. The mechanism and, in particular, the intriguing role of Sc³⁺ as mediator in the TPPO electroreduction been uncovered by density functional theory calculations.     

Nature of the complexes formed by alkali metal halides with phosphine oxides

Reaction of alkali metal halides (MX) with methylenediphosphine oxides and various related compounds in nonaqueous solutions leads to the formation of complex compounds. The compositions, properties, and stabilities of these compounds, which have been studied in detail in acetonitrile, are determined by the nature of the cations and anions of the alkali metal halides. Formation of neutral complexes with the composition [MX · L] and cationic complexes with the composition [ML]⁺ has been established. The most characteristic representative of complexes of the first type is [NaI · L]; in the complexes studied, L=R₂P(O)CH₂P(O)R₂ (R=Bu, BuO, or Ph), Ph₂P(O)CH₂P(O) (OC₂H₅)CH₂P(O)Ph₂ and (p-OCH₃C₆H₄)₂P(O)CH₂P(O)(C₆H₄CF₃-p)₂. Compound [LiL]⁺ is characteristic of complexes of the second type; the compounds containing Ph₃P(O), Ph₂P(O)CH₂P(O)Ph₂, and Ph₂P(O)CH₂P(O)(OC₂H₅)CH₂P(O)Ph₂ as ligands have been studied. Stability constants of the complexes [NaI · L] and [LiL]⁺ have been determined by measuring the dependence of the electrical conductivity of solutions of the alkali metal halides in acetonitrile on the concentration of the ligands. The complex-forming power of phosphine oxides increases with increase in the number of P=O groups. Stabilities of the complexes [NaI · L] with ligands with identical structure decrease with increase in the electronegativity of the substituents on the phosphorus atoms.     

Structures and Unexpected Dynamic Properties of Phosphine Oxides Adsorbed on Silica Surfaces

Solid‐state NMR spectroscopy of selected phosphine oxides adsorbed on silica surfaces establishes the surface mobilities, even of phosphine oxides with high melting points. Crystal structures of the adducts Ph₃PO ? HOSiPh₃ and Cy₃PO ? H₂O indicate that the interactions with silica involve hydrogen bonding of the P?O group to adsorbed water and surface silanol groups.     

Synthese und Kristallstrukturen von [(Ph3As)2CCN–MnBr3], [(Ph3As)2CCN–CoBr3] und [(Ph3As)2CCN]+CuBr2–

Syntheses and Crystal Structures of [(Ph₃As)₂CCN–MnBr₃], [(Ph₃As)₂CCN–CoBr₃], and [(Ph₃As)₂CCN]⁺CuBr₂^– The di(arsa)acetonitrilium bromide [(Ph₃As)₂CCN]Br reacts with the anhydrous dibromides of manganese and cobalt in acetonitrile to form the molecular complexes [(Ph₃As)₂CCN–MBr₃] [M = ( 1 ), Co( 2 )] with zwitterionic structures. With copper(I)bromide, however, the ionic compound [(Ph₃As)₂CCN]⁺CuBr₂^– ( 3 ) is formed. All complexes are characterized by IR spectroscopy and by crystal structure analyses. 1 and 2 crystallize isotypically with each other in the space group P 1 with two formula units per unit cell. The MBr₃^– fragments in the molecular complexes are connected to the N atom of the [(Ph₃As)₂CCN]⁺ cation showing bond angles C–N–Mn of 156.9° and C–N–Co of 161°, and distances Mn–N of 215.6 pm and Co–N of 201 pm. In 3 , on the other hand, (space group C2/c, Z = 4) the ions [(Ph₃As)₂CCN]⁺ and the linear Br–Cu–Br^– ion are to be found concurrent but separate.     

Stabilized Carbenium Ions as Latent,Z‐type Ligands

Controlling the reactivity of transition metals using secondary, σ‐accepting ligands is an active area of investigation that is impacting molecular catalysis. Herein we describe the phosphine gold complexes [(o‐Ph₂P(C₆H₄)Acr)AuCl]⁺ ([ 3 ]⁺; Acr=9‐N‐methylacridinium) and [(o‐Ph₂P(C₆H₄)Xan)AuCl]⁺ ([ 4 ]⁺; Xan=9‐xanthylium) where the electrophilic carbenium moiety is juxtaposed with the metal atom. While only weak interactions occur between the gold atom and the carbenium moiety of these complexes, the more Lewis acidic complex [ 4 ]⁺ readily reacts with chloride to afford a trivalent phosphine gold dichloride derivative ( 7 ) in which the metal atom is covalently bound to the former carbocationic center. This anion‐induced Au^I/Au^III oxidation is accompanied by a conversion of the Lewis acidic carbocationic center in [ 4 ]⁺ into an X‐type ligand in 7 . We conclude that the carbenium moiety of this complex acts as a latent Z‐type ligand poised to increase the Lewis acidity of the gold center, a notion supported by the carbophilic reactivity of these complexes.     

Stabilized Carbenium Ions as Latent,Z‐type Ligands

Controlling the reactivity of transition metals using secondary, σ‐accepting ligands is an active area of investigation that is impacting molecular catalysis. Herein we describe the phosphine gold complexes [(o‐Ph₂P(C₆H₄)Acr)AuCl]⁺ ([ 3 ]⁺; Acr=9‐N‐methylacridinium) and [(o‐Ph₂P(C₆H₄)Xan)AuCl]⁺ ([ 4 ]⁺; Xan=9‐xanthylium) where the electrophilic carbenium moiety is juxtaposed with the metal atom. While only weak interactions occur between the gold atom and the carbenium moiety of these complexes, the more Lewis acidic complex [ 4 ]⁺ readily reacts with chloride to afford a trivalent phosphine gold dichloride derivative ( 7 ) in which the metal atom is covalently bound to the former carbocationic center. This anion‐induced Au^I/Au^III oxidation is accompanied by a conversion of the Lewis acidic carbocationic center in [ 4 ]⁺ into an X‐type ligand in 7 . We conclude that the carbenium moiety of this complex acts as a latent Z‐type ligand poised to increase the Lewis acidity of the gold center, a notion supported by the carbophilic reactivity of these complexes.     

Stereochemically controlled synthesis of unsaturated acids via diphenylphosphinoyl (Ph2PO) -ketoacids

Acylation of phosphine oxide anions with derivatives of cyclic anhydrides or oxidative cleavage of cyclic allyl phosphine oxides gives Ph₂PO-ketoacids: reduction, separation of diastereoisomers, and completion of the Horner-Wittig reaction gives single isomers ($\text{E}$) or ($\text{Z}$) of unsaturated acids.     

Reaktion von Phosphinboran,Phenylphosphinboran und Phosphoniumjodid mit Natriumtetrahydridoborat

Zusammenfassung Phosphinboran und Phosphoniumjodid reagieren mit NaBH₄ unter H₂-Entwicklung zu H₂P(BH₃)₂–Na⁺(I), Phenylphosphinboran zuPhHP(BH₃)₂–Na⁺ (II). Methylphosphinboran, Phenylphosphin und die Anionen von I und II reagieren nicht mit NaBH₄, da die Acidität des an Phosphor gebundenen Wasserstoffs zu gering ist. Auch (PhHP·BCl₂)₃ reagiert mit NaBH₄ unter Wasserstoffentwicklung.

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Reaction of phosphine borane, phenylphosphine borane and phosphonium iodide with sodium tetrahydridoborate

The reaction of phosphine borane and phosphonium iodide with NaBH₄ yields H₂P(BH₃)₂–Na⁺ (I), of phenylphosphine boranePhHP(BH₃)₂–Na⁺ (II) hydrogen being evolved in both reactions. Methylphosphine borane, phenylphosphine and the anions of I and II do not react with NaBH₄ on account of the reduced acidity of the hydrogen atoms bound to phosphorus. Likewise hydrogen is evolved if (PhHP·BCl₂)₃ reacts with NaBH₄.

     

Synthesis of a stable,foamable, gold-containing organic carboxylate polymer

The functionalized polyethylene acrylic acid copolymers Primacor 1430 (P1430, containing 9.5% acrylic acid) and Primacor 5980 (P5980, containing 20% acrylic acid) have been used to synthesize gold/polymer dispersions and gold/polymer ionomers, respectively. When [Ph₃PAu]⁺ is bonded directly to the carboxylate, work-up of the polymer leads to decarboxyation and metallic gold formation. However, ionic bonding of [(Ph₃P)₂Au]⁺, and related bis phosphine cations produce workable, foamable polymers. Analysis shows samples from these reactions to contain between 4–15 wt % of Au depending on the type of gold complex used and the reaction conditions. The gold/polymer (ionomer) sample with about 12% Au has been worked to mold sheets of foam. © 1993 John Wiley & Sons, Inc.     

Preparation and properties of novel palladium compounds containing a thiomethoxymethyl group

Oxidative addition of chloromethyl methyl sulfide to Pd(Ph₃P)₄ provided a good yield of Pd(Ph₃P)₂(CH₂SCH₃)Cl (I) whose ¹H NMR and molecular weight data showed that dissociation of either the phosphine or the chloride ligand occurs in CH₂Cl₂ solution. In accord with such equilibria, repeated crystallization of I from CH₂Cl₂ and Et₂O gradually removed the triphenylphosphine set free in these solvents to give the monomeric complex. Pd(Ph₃P)(CH₂SCH₃)Cl (III), while treatment of 1 with NH₄PF₆ in CH₂Cl₂ and acetone gave the cationic complex [Pd(Ph₃P)₂(CH₂SCH₃]PF₆ (II),¹H NMR spectra of II and III are discussed in terms of a three-membered chelate structure arising from coordination of sulfur with palladium     

New synthetic “tricks”. Triphenylphosphine-mediated amide formation from carboxylic acids and azides

Equimolar amounts of carboxylic acids, aryl or alkyl azides, and Ph₃P in refluxing benzene (hexane, toluene) afford amides in good yields. Insolubility of zwitterions Ph₃P⁺-NH(CH₂)_nCOO-, arising from μ-azido acids and Ph₃P, limits the utilization of the method for lactame formation.     

Gas phase ion/molecule reactions in phosphine/germane mixtures studied by ion trapping

Gaseous mixtures of phosphine and germane have been investigated by ion trap mass spectrometry. Reaction pathways together with rate constants of the main reactions are reported. The mechanisms of ion/molecule reactions have been elucidated by single and multiple isolation steps. The GeH_n⁺ (n = 1–3) ions react with phosphine to give GePH_n⁺ (n = 2–4) ions. The GePH₄⁺ ion further reacts with GeH₄ to yield Ge₂PH₆⁺. The GePH_n⁺ (n = 2–4) mixed ionic family also originates from the P⁺ phosphine primary ion, as well as from the P₂H_n⁺ (n = 0–3) secondary ions of phosphine reacting with neutral germane and from Ge₂H₂⁺ reacting with phosphine. The main reaction pathways of the PH_n⁺ (n = 0–2) ions with GeH₄ lead to the formation of the GeH₂⁺ and GeH₃⁺ ionic species. Protonation of phosphine from different ionic precursors is a very common process and yields the stable phosphonium ion, PH₄⁺. Trends in total abundances of secondary GePH_n⁺ (n = 2–4) ions as function of reaction time for different PH₃/GeH₄ pressure ratios show that excess of germane slightly affects the nucleation of mixed Ge-P ions.     

31P CP-MAS NMR,Vibrational, and X-Ray Characterization of the Adducts of Triphenylphosphine Sulfide with ICl and IBr

The reactions between triphenylphosphine sulfide (Ph₃PS) and ICl in CCl₄ and IBr in CH₂Cl₂ in 1 : 1 molar ratio give the solid adducts Ph₃PS · ICl ( I ) and Ph₃PS · IBr ( II ) whose structures have been solved by X-ray diffraction. Compounds I and II consist of discrete molecule units and feature the S–I–Cl or S–I–Br linear group. The S–I bond distances in I , II (2.641(1), 2.665(1) Å respectively) and in compound 2 Ph₃PS · 3 I₂ ( III ) (2.729(2) Å) are correlable to the net increase in the I–X (X = Cl, Br, I) bond distance. The structural features of I , II and III are in accordance with ³¹P CP–MAS NMR, FT-Raman and FT-IR spectral data, and elucidate the nature of the donor (Ph₃PS)-acceptor (ICl, IBr, I₂) interaction.     

In the footsteps of August Michaelis: Syntheses and Thermodynamics of Extremely Low-Volatile Ionic Liquids

A series of nine different known ionic liquids or low melting salts was synthesised and purified. They are composed of the [NTf₂]^– (bis(trifluoromethane)sulfonimide), [OTf]^– (trifluoro-methane-sulfonate), or [B(CN)₄]^– (tetracyanidoborate) anion and [Ph₄P]⁺ (tetraphenylphosphonium), [Ph₃BzP]⁺ (triphenylbenzyl phosphonium), [ⁿBu₄P]⁺ (tetra-ⁿbutylphosphonium), [ⁿBuPh₃P]⁺ (tri-phenyl-ⁿbutylphosphonium), [ⁿBu₄N]⁺ (tetra-ⁿbutylammonium), or the [PPN]⁺ (bis(triphenylphosphine)iminium) cation. Precise vapour pressure data and enthalpies of vaporisation were measured using the Quartz Crystal Microbalance (QCM) method and evaluated. Structure-property relations are established using the obtained data as well as literature known data of ILs with alkyl-substituted imidazolium cations. It turns out that ILs with the tetracyanidoborate anion have even higher values of the enthalpy of vaporisation than those with the common [NTf₂]⁻ or [OTf]⁻ anion and therefore are even less volatile.     

Syntheses and Crystal Structures of Copper and Silver Complexes with the Ylide Ph3PCHP(O)PPh2 as Ligand

The reactivity of the hydrolysis product of hexaphenylcarbodiphosphorane, PPh₃CHP(O)Ph₂, towards different soft Lewis acids, such as CuI and Ag[BF₄] are reported. While CuI exclusively binds at the ylidic carbon atom, reaction of the silver cation in CH₂Cl₂ leads to proton abstraction from the solvent to give the cation [PPh₃CH₂P(O)Ph₂]⁺. Surprisingly, Ag⁺ replaces the methyl group of [PPh₃CHMeP(O)Ph₂]⁺ to produce a dimeric complex, in which Ag⁺ is coordinated to C and O forming an eight membered ring. The compounds were characterized by spectroscopic methods and X‐ray diffraction.     

The hydrolysis of dibromofluoromethyltriphenylphosphonium bromide

Hydrolysis of [Ph₃$\text{P}\text{+}$PCFBr₂]Br^? afforded a high yield of dibromofluoromethane and triphenylphosphine oxide. Hydrolysis in the presence of a radioactive isotope of bromine gave evidence that the mechanism of this reaction proceeds $\text{via}$ the dibromofluoromethide ion and not $\text{via}$ a bromofluorocarbene intermediate.